Aerobic treatment – August 2019

- Organization : IFRC
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Description du contexte d’urgence
Community (dimension, livelihood, type of shelter/house, HHs dimension)
Living area of community (name and localization of camp/city/village, access)
Other WaSH activities implemented in the community
Local and international WaSH institutions (management committees, NGOs, WaSH governmental agencies, private sector) with WaSH active role in the community and specific partnerships
Main waterborne diseases
Les indicateurs
Le récit
The anaerobic baffled reactor is used as pretreatment, to remove solids from the waste stream. The waste then moves to two reactor tanks in series. The aeration of the incoming faecal sludge in the a reactor tanks leads to the breeding of bacteria that metabolize the organic content (COD/TOC (Total Organic Content)) together with the oxygen, turning the organic content into a gas (carbon dioxide).
The supernatant from the two reactor tanks is transferred to a settling tank, where the remaining solids are separated. The supernatant of the settling tank is then passed through a glass bead filter, which is regularly backwashed, for the removal of parasites and parasite eggs. Finally, the liquid is disinfected by chlorine or UV. Sludge from the settling tank is added to the reactor tank. Reactor tank sludge is treated by anaerobic digestion or lime treatment.
The plant is located next to a creekline that has been widened. The site has yet to be flooded, however potential flooding could occur in large rainfall event (e.g. 1 in 50 years).
The unit does not produce strong odours or attract insects but it should be as far from settlement as possible while still allowing for efficient delivery of faecal waste.
Fencing and security are needed for health and safety and theft prevention.
A fully functional faecal sludge quality laboratory is a requirement for this unit.
The cost is $180,000 per treatment line ($9.00 per person) excluding works, plus local materials (e.g.fencing, gravel). It includes genset rather than renewable energy source.
The skills required for set up and oversight is aerobic treatment expertise.
The construction lasts 2-5 days and the inception time is about 4 weeks or more depending on waste characteristics.
Equipment package comes with 12 kVA genset and wiring for connection to renewable energy. Water is needed for inception and backwash.
An estimated 0.1 m3 of dried sludge and 10 m3 of treated wastewater is discharged per day (wastewater can safely be used for irrigation or added to a surface waterway).
There is a 2.2m3 inflow every day, and 2.5m3 of output is produced every 3 days, with a 10% solids (100 kg / m3).
The COD average influent concentration is 23,600 mg/L and the COD average effluent concentration is 1,100 mg/L.
The faecal coliforms are fully removed due to current chlorination dosage.
The average TS influent concentration is 22 g/kg and the outlet concentration is 5 kg//kg.
The average pH for influent is 8.1 and the average pH for effluent is 7.9.
The helminth eggs average influent concentration is 266 eggs/g and the helminth eggs average effluent concentration is 3 eggs/g.
The cost is $5 per m3 treated, reduced with use of renewable energy. It excludes sludge transport cost.
The skills required for daily operation and maintenance is basic mechanical and electric skills and low skill labour.
The aerator and oloid are coming from Germany, the oxfam tanks are also imported from abroad.
Forces
- Odour and solid reduction
- Low land use
- Effective and efficient
Faiblesses
NC